Centrifugal oil separator for removing oil from a waste flowing stream

ABSTRACT

An oil separator for removing oil from a flowing waste stream of waste fluid includes: a separator body having a flow bore with a center, an open bottom and an open top each communicating with the flow bore so that fluid can flow in the flow bore between the open bottom and the open top; and a plurality of vanes, each defining a spiral path for fluid flowing in the bore between the open bottom to the open top, the vanes being spaced radially from the center of the bore and each vane having upper and lower end portions. Each vane has a surface to which oil particles can adhere and coalesce as the oil particles travel upwardly thereupon, and the vanes are positioned in the bore with the upper and lower end portions of each vane communicating respectively with the bore open top and the bore open bottom portions (i) to swirl waste fluid upwardly, creating laminar flow, (ii) to centrifugally force the waste fluid outwardly in a direction away from the bore center, and (iii) to separate oil particles from the wastewater stream beginning with the vane end portions that receive influent wastewater flow. A separator is positioned adjacent the bore for separating oil collected and coalesced on the vanes from the wastewater stream.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of pending U.S. PatentApplication Ser. No. 902,592, filed Sept. 2, 1986 now U.S. Pat. No.4,737,282, which is a continuation-in-part of U.S. Patent ApplicationSer. No. 648,497, filed Sept. 10, 1984, now U.S. Pat. No. 4,626,360.

BACKGROUND OF THE INVENTION:

1. Field of the Invention:

The present invention relates to the treatment of a waste water streamcontaining water, oil, sand, oily sand and gas to separate the oil,sand, gas and water out of the waste water stream. In particular, thepresent invention is related to a method and apparatus for use onoffshore and onshore oil and gas well drilling operations whereby thewater and sand can be purified to a point at which it can be releasedinto the environment without damaging the environment.

2. Description of the Prior Art

Most oil and gas wells both onshore and offshore produce a large amountof waste water which commonly contains oil, gas and sand. The sandcontained in the waste water stream frequently is contaminated or soakedwith oil to the extent that the sand cannot be discharged into theenvironment because of the environmentally dangerous levels of oilcontained in the sand. Most state and federal regulations now requirethat waste water and sand discharge into the environment meet certainmaximum limitations on the amount of oil contained therein.

U.S. Pat. No. 4,198,300 discloses an apparatus for removing suspendedoil droplets from water, including a vertical pipe suspended from anoffshore oil platform partially submerged in the sea surrounding theplatform, a means for injecting a waste water stream into the middleportion of the pipe and a means for injecting gas into the lower portionof the pipe and for diffusing the gas to disperse the gas into gasbubbles, so that the gas bubbles counter currently contact the wastewater stream as the gas bubbles rise to the upper portion of the pipe,thereby attaching the oil droplets and reducing the overall density ofthe oil droplets efficiently so that the upper velocity of the oildroplets is greater of the downward velocity of the waste water streamand promoting the separation of oil droplets from the waste waterstream, and means for withdrawing the oil droplets from the upperportion of the pipe. The apparatus uses natural gas air or inner gas asthe gas medium for forming the gas bubbles.

U.S. Pat. No. 4,221,671 discloses an upright circular tube settler withstacked tube modules for removal of solids from fluids and for removalof one fluid from another. The tube modules are for use in a tubesettler of the type having vertically disposed concentric tubular walls.The modules contained concentric rows of essentially straight fluid flowpassages open at both ends, the passages in each row of a particularmodel being tilted relative to the vertical in the same direction and tosubstantially the same degree, the passages in each row being skewed inrelation to other passages in the same row of the same tier. Thepassages cooperate to provide means for directing fluid in asubstantially spiral path around a tank.

U.S. Pat. No. 4,217,211 discloses a sewage treatment process whereinsewage is passed into deep underground shaft and is improved by passinga liquor of the sewage in the underground shaft through an inner shaftwhich extends only part way down into the underground shaft. A mixingshaft and liquor nozzles are provided for receipt of the sewage liquorpassing downwardly. The action of the descending liquor through thenozzles entrains ascending liquor from the shaft into the descendingliquor resulting in recirculation which allows extended contact time ofthe liquor with a microorganisms used to digest the sewage.

U.S. Pat. No. 4,186,087 discloses a method and apparatus for separatingsubstances from liquids by flotation using bubbles comprising absorbinga substance present in a liquid on bubbles, floating the bubblesabsorbing the substances and separating the substance from the bubbles,characterized by allowing the bubbles absorbing the substance to ascendthrough a fluid route in a tube independent of the ambient turbulentlyflowing liquid and then collecting and separating the substance from theliquid at the upper end of the tube. The apparatus includes a verticalcolumn provided at the bottom with a gas-diffusing means and a tubeplaced inside the vertical column, the tube being provided with a meansfor collecting bubbles at the lower end and concentrating in thecollected bubbles at the upper end.

U.S. Pat. No. 4,066,540 comprises a vertical column for continuous frothflotation having therein a froth separator, a raw water inlet pipe, atreated water discharge pipe and gas dispersing unit, and steppedshelves disposed inside the column and adapted to provide thoroughcontact between the bubbles and water subjected to treatment.

U.S. Pat. No. Re. 28,378 discloses an apparatus for effectingpurification of liquids by flotation wherein a mixture of gas in liquidis subjected to sufficient pressure for the gas to dissolve in theliquid and to form a solution of the gas in the liquid. The solution isintroduced into a flotation tank and pressure is lowered to form gasbubbles in the tank at a slow rate, thereby forming very small bubbles.The slow rate at which the very small gas bubbles are formed providespurification of polluted liquids by flotation.

U.S. Pat. No. 3,893,918 discloses a method for separating materialsleaving a well including utilizing an elongated separator conduitpartially above and below the surface of a body of water to establish afluid column in the water, supplying an oil containing fluid mixture inthe fluid column and causing the fluid to float downwardly through aflowing zone over a plurality of baffle means to induce coalescentseparation of oil from fluid, intermittently interrupting the supply offluid to impede the downward velocity of fluid for a time sufficient foroil to rise from the flowing zones into the quiescent zones defined bythe baffles, flowing oil accumulated in the quiescent zones upwardly toestablish an upper layer of oil in the fluid column, flowing oilaccumulated in the lower quiescent zones through the upper quiescentzones, withdrawing oil from the upper oil layer, and flowing the oilfree liquid from the exit zone of the separator from the body of waterbeneath the surface thereof.

U.S. Pat. No. 3,520,415 discloses a separation vessel disposed in avertical column for separating a hydrocarbon material from a slurry ofwater, bitumen, and sand. The vessel includes a impeller mechanism, asand settling zone, and a froth disengaging zone. A set of turbulencereducing baffles is mounted between the underwash sparger and the frothwithdrawal conduit.

U.S. Pat. No. 2,806,599 discloses a vacuum control for gravityseparators utilized for effectively recovering extremely fine fractionsof sand suspended in water utilizing a low pressure cyclone gravityseparator whereby fluids are spiraled about in a cyclone in a circularmanner to separate solids such as sand from the fluids.

U.S. Pat. No. 2,754,980 discloses a fluid separator for separatingsolids or liquid particles from fluids. The separator is disposed in avertical manner and contains no moving parts. The fluid is helicallywhirled in a stream so that the particles become centrifugallyconcentrated in the outer peripheral regions of the stream, the fluidstream opening tangentially into the upper end of a vertical casing, awell inside with the lower end open to the interior of the casing andupper open exterior of the casing, means in the well for impressing ahelical path upon the fluids stream passing from the bottom to the topof the well, and an ejecter zone intermediately at the end of the well.

U.S. Pat. No. 1,869,241 discloses a vertical apparatus for theseparation of the solid substances, such as for separating the graphitefrom its ore by the emulsion process. The fluids flows through a centralpipe and into a series of baffles to effect separation of solids fromthe fluid.

U.S. Pat. No. 1,458,805 discloses an apparatus for the settlement ofsolid particles in suspension in liquids and discloses a vertical columnhaving a series of baffles therein, and a number of parallel slopingsettling surfaces separated by similar settling spaces to separateparticles from a liquid stream flowing therethrough.

U.S. Pat. No. 3,359,357 discloses a process and apparatus for refininghydrocarbons which includes a vertical column having an inclined spiralplate over which the fluids are flowed.

The above patents disclosed various separation and flow treatmentdevices but none show the novel combination of elements provided forseparating oil, gas, sand and water in a waste water stream disclosed inthe present invention.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided an apparatusfor separating oil, gas and sand from a waste water stream and forseparating oil from oily sand and the waste water stream including anupper oil manager assembly for collecting and conveying oil separatedfrom a waste water stream, a sand helix assembly connectable to theupper oil manager assembly for separating sand particles and oilparticles from a waste water stream, a sand manager assembly connectableto the sand helix assembly for collecting sand separated from the streamof waste water and removing oil from the sand, a flow control assemblyconnectable to the sand manager assembly for controlling the flow ofoil, water and sand through the apparatus, a lower oil manager assemblyconnectable to the flow control assembly for receiving oil andtransferring oil to a storage facility outside of the apparatus, and anoil helix assembly connectable to the lower oil manager assembly forseparating oil from the waste water stream.

The present invention has the advantage over the prior art of much morethoroughly cleaning a waste water stream. Furthermore, the invention canbe made in module form so that the degree of cleanliness of the effluentcan be varied depending upon the number of sand helix and oil helixmodules added to apparatus.

In addition, the present invention can remove oil from sand to a higherdegree of purity, thereby enabling sand previously contaminated with oilto be discharged into the environment without damaging the environment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic elevational view, partially in section, showing anoffshore production platform including the separation apparatus of thepresent invention;

FIG. 2 is a schematic elevational view, partially in section, showing anoil helix module of the present invention;

FIG. 3 is a cross-sectional view taken along lines 3--3 of FIG. 2;

FIG. 4 is a schematic, partially cross-sectional view of the water worksexecutive or flow control assembly of the present invention;

FIG. 5 is schematic elevational view, partially in section, of the sandmanager of the present invention taken along lines 5--5 of the FIG. 6;

FIG. 6 is a cross-sectional view of FIG. 5 taken along lines 6--6 ofFIG. 5;

FIG. 7 is a schematic elevational view, partially in section, showing asand helix module of the present invention;

FIG. 8 is a cross-sectional view taken along lines 8--8 of FIG. 7;

FIG. 9 is a schematic elevational view, partially in section, showingthe upper oil manager of the present invention;

FIG. 10 is a schematic elevational view, partially in section, showingthe lower oil manager of the present invention;

FIG. 11 is a schematic elevational view, partially in section, showingan alternate embodiment of an oil helix module of the present invention;

FIG. 12 is a cross-sectional view taken along lines 12--12 of FIG. 11;

FIG. 13 is a schematic elevational view, partially in section, showingan alternate embodiment of the sand helix module of the presentinvention; and

FIG. 14 is a cross-sectional view taken along lines 14--14 of FIG. 13.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, in FIG. 1 is shown the separator of thepresent invention generally indicated by the numeral 20 connected tooffshore platform 22 located in a body of water 24 in a manner similarto that described in U.S. Pat. No. 4,198,300. Platform 22 is a fixed,bottom supported structure typical of those used for offshore drillingand production and is fabricated from a plurality of welded membersincluding legs 26, cross braces 28 and diagonal braces 30. Thestructural members provide the platform with the strength necessary tosupport platform deck 32 and withstand the wind, waves and sea currentencountered in an offshore environment.

As shown in the drawing, platform 22 is a production platform capable oftreating and storing the fluids such as oil and gas produced from anearby offshore field. Rising from the sea floor 34 are a series of wellpipes or conductors 36 which transport oil and gas produced from severalwell sites located within the offshore field. Platform 22 serves as acentralized collection and processing facility for the field.

Since fluids produced from oil fields frequently contain significantquantities of water in addition to oil and gas, the production facilitymust be equipped to segregate the oil, gas and water mixtures into theirconstituents. Platform deck 32 is shown in the drawings equipped withthe components and apparatus necessary to substantially separate theproduced fluids. Fluids from the well pipes 36 flow into gas separator38 which separates the fluids into their liquid and gaseous components.Separator 38 is essentially a high pressure settling tank which permitsthe lighter hydrocarbon components, primarily methane, to flash off andseparate from the heavier liquid components and to be withdrawn throughgas line 40.

Liquid components from separator 38 then enter treater 42 whichseparates the liquids into an oil stream 44 and a waste water stream 46.Pump 44a pumps the oil stream 44 to land or a reservoir through pipeline44b. Treater 42 is typically a heater-treater which simultaneously heatsand separates the oil and waste water mixture. The application of heatto the liquid stream assists in destabilizing the oil-water mixture.Demulsifying agents can also be added at this point to help break anyoil-water emulsion which may have formed as a result of excessive mixingof the oil and water components. The separation unit of the treater mayconsist of a combination of weirs, coalesces, baffles and skimmers whichserve to gravitationally separate the oil-water mixture.

Normally, treater 42 can substantially separate the oil-water mixture.However, such separation equipment at best will typically discharge awaste water stream which contains anywhere from 200 to 1000 parts permillion of oil. Since the waste water effluent from an offshore rig mustultimately be discharged into the sea and the waste water from an inlandrig must be discharged onto land, the oil content of the effluent has tobe reduced even further to satisfy environmental regulations.

The apparatus and method of the present invention are employed toprovide the necessary secondary treatment to waste water stream 46 toreduce its oil content and the amount of oil on sand to anenvironmentally acceptable level and to maximize recovery of oil fromthe offshore field. The separator apparatus of the invention isgenerally indicated by the numeral 20 and is vertically positioned inplatform 22. As can be seen in FIG. 1, separator 20 extends from theposition above the surface of the sea to a position substantially belowthe surface. Separator 20 should be securely attached to or supported byplatform 22 so that it remains in a stable position even when under theinfluence of strong wind, wave or current action. For example, separator20 can be bolted or welded to the legs and braces 28 and 30 to providethe necessary structural support.

It should be noted that for purposes of the present invention, platform22 to which separator 20 is secured need not be a fixed, bottomsupported platform of the type shown in the drawings. Separator 20 canbe supported by any type of offshore rig or structure which can be usedfor oil and gas production purposes. Such offshore rigs includeconventional offshore production structure such as jackup rigs, concreteplatforms, monopods and guyed towers. Moored production vessels adjacentbuoyed production risers can serve to support the apparatus of thepresent invention. Furthermore, the separator of the invention could beutilized above sea level or onshore just as effectively.

The lower end of separator 20 is typically open to the sea at the bottomend 90 to permit the discharge of clarified waste water. If theseparator were being used on land, a pipe or hose could be connected tolower end 90 to convey clarified waste water to any desired location.Gas is supplied to separator 20 from gas line 40 and waste water issupplied to separator 20 by line 46.

Separator 20 is composed of several separate components. Thesecomponents include, beginning at the top of the embodiment of theseparator shown in FIG. 1, an upper oil manager generally indicated bythe numeral 60 in FIGS. 1 and 9 which collects oil from the sand helix48 and conveys it to the lower oil manager 54; a sand helix generallyindicated in FIGS. 1, 7 and 8 by the numeral 48 which processes thetotal water stream, separating solid (sand) particles from the oil-waterstream in a counter current fashion, and separating some oil from thestream; a sand manager generally indicated in FIGS. 1, 5 and 6 by thenumeral 50 which collects sand particles separated from the stream ofwater by the sand helix in a reservoir contained therein for furthertreatment; a water works executive generally indicated in FIGS. 1 and 4by the numeral 62 which includes the controls, valves, meters and thelike to control the oil, water, gas and sand flow between the variouscomponents; a lower oil manager generally indicated by the numeral 54 inFIGS. 1 and 10 for transferring oil upward to a reservoir; and an oilhelix generally indicated by the numeral 52 in FIGS. 1, 2, and 3 whichprocesses the total water stream and separates oil from the stream in acounter current fashion.

In the embodiment shown in FIG. 1, all of the components are utilized incombination. However, various subcombinations of the various componentscould be utilized under certain conditions. When it is desired to treatwater containing oily sand, gas, and free oil to a point such that allparticles greater than 50 microns in size have been removed, one shouldutilize the sand helix, sand manager, water works executive, oil helix,and oil managers. If it is desired to treat water containing free oilbut a negligible amount of sand to a point where the particle size ofany particle in the stream is less than 50 microns, one could utilizeonly the oil helix, the water works executive, and the oil managers.

It can thus be seen that the separator referred to generally by thenumeral 20 may contain a combination of the above components necessaryto treat the contaminated water in a single, vertical, cylindricalenclosure or casing indicated by the numeral 58. The following is adescription of the complete system containing all the components fortreating water containing oily sand, gas, and free oil.

The separator containing the complete system is shown in FIG. 1 and isgenerally indicated by the numeral 20. At the top end of the verticalenclosure 58 containing the complete separator system 20 is the upperoil manager generally indicated by the numeral 60. The upper oil manager60 receives oil from the sand helix modules 48 below and contains a weirmechanism for controlling the level of the oil therein. As can be seenin FIG. 9, the weir mechanism includes an inverted cone 250 having avertical pipe 252 extending upward therefrom. Cone 250 and pipe areconnected to the central conduit generally indicated by the numeral 47,which extends downwardly throughout substantially the entire length ofseparator 20. All of the various elements and modules are verticallyaligned and centered on central conduit 47, which is preferably composedas a series of pipes, connected by flanges such as flanges 72 shown inFIG. 9. Oil flowing upwardly from each of the sand helix modules 48through one of the pipes 48a continues upwardly through cone 250 andpipe 252, where the oil then overflows into the space or collectionreservoir 254 between the inside of conduit 47 and the outside of cone250 and pipe 252. The oil in collection reservoir 254 is transferred tolower oil manager 54 by pipe 256. The oil traveling downwardly throughpipe 256 is driven by gas under pressure in the chamber or space 258 inthe top of separator 20.

Waste water stream (see FIG. 1) enters the separator at the executive 62and is conveyed upwardly through pipe 270. The mixture of gas, oil,sand, and water enters header 272, which is a circular pipe having holes273 therein. The mixture of gas, water, oil, and sand is sprayed fromthe header through holes 273 to effect separation of gas therefrom. Themixture of oil, water, and sand falls into the space generally indicatedby the numeral 274 between the outside of central conduit 47 and theinside of cylindrical enclosure 58.

Located immediately below the upper oil manager 60 are the sand helixmodules generally indicated by the numeral 48 as shown in FIGS. 1, 7,and 8. The sand helix modules 48 are contained within casing 58 andinclude an outer shell 64 which is generally cylindrical in shape. Thebottom of the outer shell 64 is open and has connected thereto a top 66shaped like a truncated cone.

Located in the center of shell 64 is central conduit 68 which is acontinuation of central conduit 47 and is connected thereto by flange72. Pipe 68 contains smaller pipes 48a, 88a, 256 and 270 fortransferring fluids between the various components or stages ofseparator 20. Flanges 72--72 are located at the top and the bottom ofthe sand helix module for attaching a series of sand helix modulestogether or for attaching the sand helix module 48 to another component.The top 66 is rigidly secured to central conduit 68 to prevent any fluidfrom escaping upwardly between top 66 and central conduit 68.

Located between central conduit 68 and shell 64 are a series of helicalvanes 74 held in place by a series of concentric horizontal rings 76.The rings are in turn supported by a series of concentric cylinders 78to which the horizontal concentric rings 76 are attached. The inner mostconcentric ring 80 is connected to central conduit 68.

The helical vanes 74 have a bottom edge 82 and a top edge (not shown)which are generally in alignment with the top and bottom end of outershell 64. The vanes extend from the top to the bottom of shell 64 in aspiral manner. In the embodiment shown in FIGS. 7 and 8 the helicalvanes 74 are contained in three chambers formed by the two concentriccylinders 78. The number of chambers and number of vanes may be variedas desired. The length of the vanes can be varied as desired to achievethe desired flow pattern.

In lieu of vanes, helical tubular pipes (not shown) can be alignedsimilarly to vanes 74 and held in place by a series of concentrichorizontal rings 76 (or other suitable means), generally aligned withtop and bottom of outer shell 64.

Connected to the upper end of central conduit 68 and beneath the conicaltop 66 is a baffle 84. Beneath baffle 84 is a hole 86 for intake of oilseparated from the water, sand, and oil slurry entering the base of sandhelix 48. Any oil which happens to separate in the sand helix 48 enterspipe 48a contained inside of central conduits 68 and 47 through hole 86and is conveyed upwardly to the upper oil manager 60 through pipes 48ain central conduit 47. Also located above baffle 84 is hole 88 which isthe entrance through which water exits the sand helix 48 and enters pipe88a contained inside of central conduit 68. The water entering throughholes 88 is conveyed through pipe 88a to an oil helix 52, or dischargedto the sea through the water works executive 62 shown in FIG. 4 viavalve 88h, pipe 88b, valve 88c, pipe 88d, hydrocycline 120a, flushingvessel 120c, pipe 120d, valve 120f, and discharge pipe 120g, or throughvalve 88h, pipe 88e, valve 88f and pipe 88g through the open end 90 ofseparator 20.

Thus, in operation, the sand helix module 48 receives a flow of waterdownwardly in casing 58 in the direction indicated by the arrows 92.Water flows between the inside wall of casing 58 and around the bottomof shell 64 and upwardly through vanes 74. The vanes 74, due to theirhelical shape, swirl the waste water mixture gently upward, creatinglaminar flow. Based on Stoke's Law, sand particles flow countercurrently to the oil and water stream and fall downwardly through thesand helix.

Sand falls downwardly due to its higher density (relative to water) onthe upper face of the vanes and out of the bottom of the helix asindicated by the arrows 94. Oil will rise upwardly due to its lowerdensity (relative to water) and the small droplets of oil will strikethe underside of the vanes of the sand helices, adhere, and travelupwardly along the underside of the vanes of the sand helices.Oleophyllic (oil wettable) materials (Polypropylene and the like) can beused for the vane material to enhance the efficiency of the Stoke's Lawlaw effect, which assumes that oil particles adhere to, and coalescewhen they strike a surface. Droplets may coalesce in suspension and/orwhile traveling up the vanes. The oil traveling up the vanes is forcedup and toward the center of the helix as indicated by the arrows 96 andupwardly into hole 86. Baffle 84 serves to guide the center column ofoil into hole 86. Water is forced up and outward between the vanes andtravels upwardly as indicated by arrows 98 down pipe 88a through hole88. Thus, the helically shaped vanes, in addition to Stoke's Lawseparation, centrifugally force the water and sand to the outside andthe oil to the inside, effecting a separation thereof in a favorablemanner. Sand falling from the bottom of the module is collected in sandmanager 50.

Located beneath the sand helix module 48 is the sand manager modulegenerally indicated by the numeral 50 in FIGS. 1, 5, and 6. The sandmanager 50 has a central conduit 100 in the center thereof which is acontinuation of central conduits 47 and 68 and is connected by flange102 to sand helix module 48 thereabove. Central conduit 100 is similarto central conduit 68 (see FIGS. 7 and 8) and is aligned and flangedthereto. Central conduit 100 receives and contains the various conduits270, 256, 120 and 88a for transmitting fluids and particles from onecomponent or stage of the separator 20 to another.

Rigidly connected to central conduit 100 is a cone shaped partition 103which has a horizontal ring 104 internally formed therewith. Thecombination of the cone shaped partition 103 and ring 104 forms areservoir 106 for receipt of the recovered sand slurry, indicated by thehorizontal broken lines therein.

If the sand contained in the reservoir 106 contains oil, the water jeteductors generally indicated by the numeral 108 may be utilized tothoroughly scour the oil from the oil-covered sand. Water jet eductors108 are known in the art and contain a high pressure water pipe 110which sprays water and/or stream into a venturi (hour glass) shapedsurface 112. In the separator of the present invention, water, ratherthan steam will be used. Water under high pressure is forced through theventuri 112 as indicated by the arrow 114. The high pressure watertraveling through the eductors 108 forces sand and recirculated water totravel through the eductors and to be highly agitated with the waterflowing in through pipe 110. The agitation and turbulence created withinthe reservoir 106 causes the oil clinging to the sand to be washed orstripped from the sand. The oil stripped from the sand floats up thestructure and into the sand helices 48. As the level of water and oilreaches the sand helices, the water and oil are drawn through the sandhelices.

Clean and collected in sand manager 50 is withdrawn through drain pipe116 by opening control valve 188 (see FIG. 4) and discharged overboardinto the sea. Alternatively, a slurry of water and oily sand can bewithdrawn through pipe 120 continuously when a large amount of sand isbeing separated. After being scoured by the eductors 108, oil coveredsand is removed through pipe 120, and the slurry flows into ahydrocycline 120a in the water works executive 62 shown in FIG. 4. Waterand oil flow upwardly through pipe 120b and valve 120h and sand flowsinto vessel 120c. Sand can be removed through pipe 120d and water can beintroduced through pipe 120e for flushing vessel 120c.

Located between the sand manager and the lower oil manager in a airspace with flanged headers on either side, is the water works executive62. It is an area which houses the controls, valves, meters and the liketo control the oil, water and sand flow between the various components.It is the entrance locale for the waste water stream 46, additional gasmake up stream 41, high pressure water stream 110, fresh water stream120e, and an exit point for the oil stream 282. Also, gas can be addedor removed through pipe 257. The valves for controlling the oil andwater levels by use of gas from the waste water stream 46 or fromadditional feed gas are maintained therein. The valves can be controlledby hand or electrically or pneumatically. The hydrocyclone 120a andreservoir 120c can also be located within.

Located beneath the water works executive 62 and sand manager 50 is thelower oil manager 54 shown in FIG. 1 and FIG. 10. The lower oil managerreceives oil from the upper oil manager 60 through pipes 256 and lowerstages or components through pipes 280. Lower oil manager 54 iscontained in cylindrical enclosure 58 which is closed at the upper endby flange 58a.

Lower oil manager 54 has outwardly tapered bottom walls 54a connected tovertical intermediate walls 54b and to central conduit 47. Walls 54b areconnected to inwardly sloped upper walls 54c. A vertical wall 54d isconnected to the top of wall 54c. A vertical wall 54d is connected tothe top of wall 54c. The walls 54a-54d form a reservoir for holding oilindicated by the horizontal broken lines therein. As can be seen in FIG.10, gas in the top of the lower oil manager 54 can be removed or addedthrough pipe 257 and valve 257a to control the level of the oil pad 310.Oil contained in oil manager 54 is pumped through pipe 282 by pump 284to a storage tank 49 on the surface 32 of the platform 22.

Located beneath lower oil manager 54 is an oil reservoir generallyindicated by the numeral 300 having a series of holes 306 therein. Hereoil, having risen through pipe 304 from oil helices 52 (see FIGS. 2, 3and 10), accumulates as a thick oil pad 310 between central conduit 47and outer casing 58 which floats on the water 400 in casing 58. Positivepressure is maintained in this whole lower half of separator 20 becauseof the continuous addition of gas through pipe 40 to lift oil from theoil pad 310 to the lower oil manager 54, and by venting any excessthrough pipe 257.

Thus, this oil "pad" or reservoir is maintained at a level equal to orslightly lower than minimum sea level. To circumvent the typicalproblems incurred with "blowcases" or submerged pumps, pipe 306aconnected to hole 306b take suction at the oil pad and physicallytraverses downward through the central conduit 47 for a calculateddistance, elbows upward for 180 degrees into pipe 280, and rises in pipe280 all the way up central conduit 47 past the suction level to thelower oil manager 54 (see FIGS. 3 and 10). Gas line 40 also runs downthe conduit 47 and ties in the upflow side, slightly above the lowestpoint, of the pipe 280, and utilizes what is known in the art as "gaslift" to raise the oil into the reservoir of the lowest oil manager.

Located beneath the oil pad 310 is the oil helix module generallyindicated by the numeral 52 (see FIGS. 2 and 3). The oil helix receiveswaste water from the sand helix through pipe 88a. The oil helix module52 is identical in design and construction to the sand helix previouslydescribed and shown in FIGS. 7 and 8 with the exception that the pipinginside of the central conduit indicated by the numeral 168 in FIG. 2 and68 in FIG. 7 includes pipes 40, 88a, 88g, 120g, 280, 304 and 306a. Theoil helix 52 contained within casing 58 includes an outer shell 164which is generally cylindrical in shape. The bottom of the outer shell164 is open and the top 166 is shaped like a truncated cone. Located inthe center of shell 164 is central conduit 168 which contains a seriesof smaller pipes 40, 88a, 88g, 120g, 280, 304, and 306a for transferringfluids between the various components and stages of separator 20.Flanges 172--172 are located at the top and the bottom of the oil helixmodule 52 for attaching a series of modules together or for attachingdifferent modules above and below. The top 166 rigidly secured to pipe168 to prevent any fluids from escaping upwardly between top 166 centralconduit 168.

Located between central conduit 168 and 164 are a series of helicalvanes 174 held in place by a series of concentric horizontal rings 176.The rings are in turn supported by a series of concentric cylinders 178to which the horizontal concentric rings 176 are rigidly attached. Theinner-most concentric ring 180 is rigidly connected to central conduit168.

The helical vanes 174 have a bottom edge 182 and a top edge (not shown)which are generally in alignment with the top and bottom ends of outershell 164. In the embodiment shown in FIGS. 2 and 3 the helical vanes174 are contained in three chambers formed by the two concentriccylinders 178. The number of chambers and number of vanes may be variedas desired. The length of the vanes can be varied as desired to achievethe desired flow pattern.

In lieu of vanes, helical tubular pipes (not shown) can be similarlyaligned similarly to vanes 174 and held in place by a series ofconcentric horizontal rings 176 (or other suitable means), generallyaligned with top and bottom end of outer shell 164.

Connected to the upper end of central conduit 168 and beneath theconical top 166 is a baffle 184. Beneath baffle 184 is a hole 186 forthe intake of oil separated and coalesced from the oil and water slurrywhich enters the oil and helix through the hole 185.

The oil separated from the oil and water stream exits the oil helix 52and enters pipe 304 contained inside of the central conduit 168 throughholes 186 and is conveyed upwardly to the oil pad 310 (see FIG. 10).Hole 185 is located above the baffle 184 and is the entrance, by pipe88a, through which the oil and water stream enters the oil helix asindicated by the arrow 185a. The oil and water mixture travels over thebaffle as indicated by the arrow 185a and encounters the helical vanes174.

Thus, in operation, the oil helix modules 52 are surrounded by a flow ofwater downwardly discharged from above the module 52 in casing 58 in thedirection indicated by the arrows 192 thus maintaining water throughoutthe casing and at the bottom of shell 164. The flow of water downwardlyfrom above the module 52 comes either from optional deck drain flowlines (not shown) on platform 32 entering casing 58 immediately belowthe oil pad 310 or from the oil helix modules 52 located above lower oilhelix modules 52. If there is only one oil helix module 52 and no deckdrains, there would be no flow down around the top of oil helix. If aplurality of oil helices 52 are used, there would be no flow down aroundthe top oil helix if there were no deck drain connections. Waterentering the oil helix 52 through entrance 185 encounters the vanes 174and swirls gently downward, remaining in the Reynold's laminar flowregime. Based on Stoke's Law, oil particles flow counter currently tothe water stream and rise upwardly through the oil helix. Oil will riseupwardly due to its lower density (relative to water) and the smalldroplets of oil will strike the underside of the vanes of the oilhelices 52, adhere, and travel upwardly along the underside of the vanesof the oil helices 52 into hole 186 as indicated by the arrows 186b. Thewater continues to travel downwardly and joins the stream 192 after itsexit from the bottom of the module. Thus the helical shaped vanes, inaddition to Stoke's Law separation, centrifugally force the water to beoutside of shell 164 and the oil to the inside of the shell, effectingthe separation of the oil-water stream in a favorable manner.

The amount of sand helix modules 48 and oil helix modules 52 may bevaried to achieve the degree of separation desired. One, two, three ormore of the sand helix modules 48 or oil helix modules 52 may beutilized. Preferably, three sand helix modules 48 and three oil helixmodules 52 are used.

Both the sand helix (or helices) 48 and the oil helix (or helices) 52must have means for causing fluids to flow therethrough in a spiral orswirling manner to separate oil and sand from water, such means having asurface to which small droplets will adhere and travel upwardly. Themeans for causing fluids to flow in a spiral or swirling manner can behollow pipes or vanes 74 and 174 arranged in the helix in a spiralconfiguration. The vanes or pipes are parallel when viewed from avertical cross-section and vertical when viewed through a horizontalcross section.

An alternate embodiment of the invention is shown in FIGS. 11 and 12,wherein the vanes 74 of sand helix 48 are replaced with helical tubularpipes 374 in sand helix 148. Sand helix 148 can be used interchangeably,or in place of, sand helix 48. Sand helix 148 is very similar to sandhelix 48 except for the substitution of pipes 374 for vanes 74,concentric rings 76, and concentric cylinders 78, and the same referencenumerals used in describing sand helix 48 will be used in the followingdescription of sand helix 148 where appropriate. The sand helix modules148 are contained within casing 58 and include an outer shell 64 whichis generally cylindrical in shape. The bottom of the outer shell 64 isopen and has connected thereto a top 66 shaped like a truncated cone.

Located in the center of shell 64 is central conduit 68 which is acontinuation of central conduit 47 and is connected thereto by flange72. Pipe 68 contains smaller pipes 48a, 88a, 256 and 270 fortransferring fluids between the various components or stages ofseparator 20. Flanges 72--72 are located at the top and the bottom ofthe sand helix module for attaching a series of sand helix modulestogether or for attaching the sand helix module 148 to anothercomponent. The top 66 is rigidly secured to central conduit 68 toprevent any fluid from escaping upwardly between top 66 and centralconduit 68.

Located between central conduit 68 and shell 64 are a series of helicaltubular pipes 374. The pipes 374 are equal in length and completely fillthe space between the shell 64 and the central conduit 68. Pipes 374 arecoiled about central conduit 68 in a helical pattern.

The helical pipes 374 have their top ends in alignment with the top endof outer shell 64. The pipes extend from the top to the bottom of shell64 in a spiral manner. The bottom ends of the pipes lie at variousdistances from the bottom of shell 64 depending on their distance fromcentral conduit 68.

The number of pipes may be varied as desired. The length of the vanes orpipes can be varied as desired to achieve the desired flow pattern.

Connected to the upper end of central conduit 68 and beneath the conicaltop 66 is a baffle 84. Beneath baffle 84 is a hole 86 for intake of oilseparated from the water, sand, and oil slurry entering the base of sandhelix 148. Any oil which happens to separate in the sand helix 148enters pipes 48a contained inside of central conduits 68 and 47 throughhole 86 and is conveyed upwardly to the upper oil manager 60 throughpipes 48a in central conduit 47. Also located above baffle 84 is hole 88which is the entrance through which water exits the sand helix 48 andenters pipe 88a contained inside of central conduit 68. The waterentering through holes 88 is conveyed through pipe 88a to an oil helix52, or discharged to the sea through the water works executive 62 shownin FIG. 4 via valve 88h, pipe 88b, valve 88c, pipe 88d, hydrocyclone120a, flushing vessel 120c, pipe 120d, valve 120f, and discharge pipe120g, or through valve 88h, pipe 88e, valve 88f and pipe 88g through theopen end 90 of separator 20.

Thus, in operation, the sand helix module 148 receives a flow of waterdownwardly in casing 58 in the direction indicated by the arrows 92.Water flows between the inside wall of casing 58 and around the bottomof shell 64 and upwardly through the pipes 374. The pipes 374, due totheir helical shape, swirl the waste water mixture gently upward,creating laminar flow. Based on Stoke's Law, sand particles flow countercurrently to the oil and water stream and fall downwardly through thesand helix.

Sand falls downwardly due to its higher density (relative to water) onthe upper face of the vanes and out of the bottom of the helix asindicated by the arrows 94. Oil will rise upwardly due to its lowerdensity (relative to water) and the small droplets of oil will strikethe underside of the vanes of the sand helices, adhere, and travelupwardly along the underside of the vanes of the sand helices.Oleophyllic (oil wettable) materials (Polypropylene and the like) can beused for the pipe material to enhance the efficiency of the Stoke's Laweffect, which assumes that oil particles adhere to, and coalesce whenthey strike a surface. Droplets may coalesce in suspension and/or whiletraveling up the vanes. The oil traveling up the vanes is forced up andtoward the center of the helix as indicated by the arrows 96 andupwardly into hole 86. Baffle 84 serves to guide the center column ofoil into hole 86. Water is forced up and outward between the vanes andtravels upwardly as indicated by arrows 98 down pipe 88a through hole88. Thus, the helically shaped pipes, in addition to Stoke's Lawseparation, centrifugally force the water and sand to the outside andthe oil to the inside, effecting a separation thereof in a favorablemanner. Sand falling from the bottom of the module is collected in sandmanager 50.

An alternate embodiment of the invention is shown in FIGS. 13 and 14,wherein the vanes 74 of oil helix 152 are replaced with helical tubularpipes 274 in oil helix 152. Oil helix 152 can be used interchangeably,or in place of, sand helix 48. Oil helix 152 is very similar to oilhelix 52 except for the substitution of pipes 274 for vanes 174,concentric rings 176, and concentric cylinders 178, and the samereference numerals used in describing oil helix 52 will be used in thefollowing description of oil helix 152 where appropriate.

The oil helix 152 contained within casing 58 includes an outer shell 164which is generally cylindrical in shape. The bottom of the outer shell164 is open and the top 166 is shaped like a truncated cone. Located inthe center of shell 164 is central conduit 168 which contains a seriesof smaller pipes 40, 88a, 88g, 120g, 280, 304, and 306a for transferringfluids between the various components and stages of separator 20.Flanges 172--172 are located at the top and the bottom of the oil helixmodule 152 for attaching a series of modules together or for attachingdifferent modules above and below. The top 166 is rigidly secured topipe 168 to prevent any fluids from escaping upwardly between top 166central conduit 168.

Located between central conduit 168 and shell 164 are a series ofhelical tubular pipes 274. The pipes 274 are equal in length andcompletely fill the space between the shell 164 and the central conduit168. Pipes 274 are coiled about central conduit 168 in a helicalpattern.

The helical pipes 274 have their top ends in alignment with the top endof outer shell 164. The bottom ends of the pipes 274 lie at variousdistances from the bottom of shell 164 depending on their distance fromcentral conduit 168.

The number of chambers and number of vanes may be varied as desired. Thelength of the vanes or pipes can be varied as desired to achieve thedesired flow pattern.

Connected to the upper end of central conduit 168 and beneath theconical top 166 is a baffle 184. Beneath baffle 184 is a hole 186 forthe intake of oil separated and coalesced from the oil and water slurrywhich enters the oil and helix through hole 185.

The oil separated from the oil and water stream exits the oil helix 152and enters pipe 304 contained inside of the central conduit 168 throughholes 186 and is conveyed upwardly to the oil pad 310 (see FIG. 10).Hole 185 is located above the baffle 184 and is the entrance, by pipe88a, through which the oil and water stream enters the oil helix asindicated by the arrow 185a. The oil and water mixture travels over thebaffle as indicated by the area 185a and encounters the helical pipes274.

Thus, in operation, the oil helix modules 152 are surrounded by a flowof water downwardly discharged from above the module 52 in casing 58 inthe direction indicated by the arrows 192 thus maintaining waterthroughout the casing and at the bottom of shell 164. The flow of waterdownwardly from above the module 152 comes either from optional deckdrain flow lines (not shown) on platform 32 entering casing 58immediately below the oil pad 310 or from the oil helix modules 152located above lower oil helix modules 152. If there is only one oilhelix module 152 and no deck drains, there would be no flow down aroundthe top oil helix. If a plurality of oil helices 152 are used, therewould be no flow down around the top oil helix if there were no deckdrain connections. Water entering the oil helix 152 through entrance 185encounters the pipes 274 and swirls gently downward, remaining in theReynold's laminar flow regime. Based on Stoke's Law, oil particles flowcounter currently to the water stream and rise upwardly through the oilhelix. Oil will rise upwardly due to its lower density (relative towater) and the small droplets of oil will strike the underside of thevanes of the oil helices 152, adhere, and travel upwardly along theunderside of the vanes of the oil helices 152 into hole 186 as indicatedby the arrows 186b. The water continues to travel downwardly and joinsthe stream 192 after its exit from the bottom of the module. Thus thehelical shaped vanes, in addition to Stoke's Law separation,centrifugally force the water to the outside of shell 164 and the oil tothe inside of the shell, effecting the separation of the oil-waterstream in a favorable manner.

The amount of sand helix modules 148 and oil helix modules 152 may bevaried to achieve the degree of separation desired. One, two, three ormore of the sand helix modules 48 or oil helix modules 152 may beutilized. Preferably, three sand helix modules 48 and three oil helixmodules 152 are used.

It should be understood that the apparatus of the invention could beused on onshore rigs, offshore rigs, or to treat any waste water streamcontaining water oil, and/or sand. Furthermore, the term "oil" caninclude any two fluids that form two phases. To utilize the apparatus ofthe invention onshore, it would only be necessary to enclose the bottomand attach a valve, pipes, and a pressure control mechanism to maintainwater and oil levels. Also, a different configuration such as twocolumns separated at the water works executive 62 with different valvesettings to maintain a similar operating environment can be used.

Although the preferred embodiments of the present invention have beendisclosed and described in detail above, it should be understood thatthe invention is in no sense limited thereby, and its scope is to bedetermined by that of the following claims.

What is claimed is:
 1. An oil separator for removing oil from a flowingwaste stream of waste fluid comprising:(a) a separator body having aflow bore with a center, an open bottom and an open top eachcommunicating with the flow bore so that fluid can flow in the flow borebetween the open bottom and the open top; (b) a plurality of vanes, eachdefining a spiral path for fluid flowing in the bore between the openbottom to the open top, the vanes being spaced radially from the centerof the bore and each vane having upper and lower end portions; (c) eachvane having a surface to which oil particles can adhere and coalesce asthe oil particles travel upwardly thereupon; (d) the vanes beingpositioned in the bore with the upper and lower end portions of eachvane communicating respectively with the bore open top and the bore openbottom portions:(i) to swirl waste fluid upwardly, creating laminarflow, (ii) to centrifugally force the waste fluid outwardly in adirection away from the bore center, and (iii) to separate oil particlesfrom the wastewater stream beginning with the vane end portions thatreceive influent wastewater flow; and (e) means positioned adjacent thebore for separating oil collected and coalesced on the vanes from thewastewater.
 2. The apparatus of claim 1, wherein the separator body isgenerally cylindrical conduit with a cylindrically-shaped bore.
 3. Theapparatus of claim 1, wherein the separator body is a cylinder with acentral longitudinal axis.
 4. The apparatus of claim 3, wherein thecentral longitudinal axis is generally vertically positioned duringoperation.
 5. The apparatus of claim 1, wherein:the center of the boreis occupied by a central portion defined by a cylinder smaller than thebody; and the vanes are spaced radially from the cylinder.
 6. Theapparatus of claim 5, wherein:the separator body is a cylinder; and thecentral portion of the bore is occupied by a smaller, concentriccylinder, and there is further provided respective oil and water outletsfor transmitting separated oil and water fluid streams into oil andwater conduits within the small cylinder.
 7. The apparatus of claim 6,wherein the separator body and the smaller, concentric cylinder share acommon central axis which is vertically positioned during operation. 8.The apparatus of claim 6, wherein:the body comprises a pair ofconcentric cylinders of large and middle size; the central portion ofthe bore is occupied by a third, smallest concentric cylinder; there isa first plurality of vanes extending between the large and middle sizedcylinder; and there is a second plurality of vanes extending from themiddle sized to the smallest cylinder.
 9. The apparatus of claim 1,wherein the separator body provides a central cylindrical bore with anaxis that is vertically positioned during operation.
 10. The apparatusof claim 1, wherein each vane provides a generally flat surface forreceiving the oil particles during separation.
 11. The apparatus ofclaim 1, wherein the plurality of vanes comprise a plurality of spirallypositioned separate conduits, each having a continuous outer wall sothat the walls of adjacent conduits are closely positioned and followsimilar spiral paths.
 12. The apparatus of claim 1, wherein theplurality of vanes define a helical path.
 13. The apparatus of claim 1,wherein the vanes each define a corresponding helical path.
 14. An oilseparator for removing oil from a flowing waste stream of waste fluidcomprising:(a) a cylindrical separator body having a bore with a center,an open bottom and an open top each communicating with the bore so thatfluid can flow between the open bottom and the open top via the bore;(b) a plurality of vanes, each defining a spiral path for fluid flowingin the bore between the open bottom and the open top, the vanes beingspaced radially from the center of the bore and each vane having upperand lower end portions; (c) each vane having a surface to which oilparticles can adhere and coalesce as the oil particles travel upwardlythereupon; (d) the vanes being positioned in the bore so that the upperand lower end portions of each vane communicate respectively with thebore open top and the bore open bottom portions:(i) to swirl waste fluidupwardly, creating laminar flow, and (ii) to centrifugally force thewaste fluid outwardly in a direction away from the bore center; and (e)wherein the body comprises three concentric cylinders of large, middle,and small size, the central portion of the bore is occupied by a thirdsmallest concentric cylinder, and there are a plurality of vanespositioned between the large and middle size cylinders and there is asecond plurality of vanes positioned between from the middle size to thesmall size.